Extender for thermosetting resin

ABSTRACT

Douglas-fir bark is prepared for use as an extender for thermosetting resins by solvent-extracting wax to leave maximum content of 3 percent.

United States Patent Inventor Frank S. Trocino Eugene, Oreg.

Appl. No. 867,360

Filed Oct. 17, 1969 Patented Oct. 26, 1971 Assignee Cascade Fiber Co.

Eugene, Oreg.

EXTENDER FOR THERMOSETTING RESIN 7 Claims, No Drawings US. Cl

106/288 Q, 117/148,117/165,161/162, 161/168, 260/17.2 R, 260/173 R, 260/209 Int. Cl ..C08g51/18, C08h 17/18 Field 01' Search 260/9, 17.2,

OTHER REFERENCES Plastics, Aug. 1947, pp. 44, 65- 67, Douglas-Fir Bark Utilized as a Filler, Marple Tappi, Apr. 1950, Vol. 33, No. 4, pp, 183- 186, Wax From Douglas-Fir Bark," Kurth et al.

Primary Examiner-William H. Short Assistant Examiner-Edward Woodberry Attorney-Buckhorn, Blore, Klarquist and Sparkman ABSTRACT: Douglas-fir bark is prepared for use as an extender for thermosetting resins by solvent-extracting wax to leave maximum content of 3 percent.

EXTENDER FOR THERMOSETTING RESIN BACKGROUND OF THE INVENTION In the formation of cellulosic products such as plywood and bonded-fiber products such as hardboard, softboard, wallboard and the like, it has been the practice to mix a thermosetting adhesive with a filler or extender. lncluded amongst the extenders which have been utilized heretofore is finely ground Douglas-fir bark, great quantities of which are available and which, for the most part, have been a waste product presenting a disposal problem. However, raw Douglas-fir bark has only been used to a limited extent because of difficulties heretofore encountered in its usage. To obtain a satisfactory adhesive material it has been necessary to cook the resin and raw fir bark for periods up to several hours, and difficulty has been encountered in determining a proper termination time for such cooking. Thus, although vast quantities of the bark have been available, and it would provide a low cost source of extender, only very limited use of the bark as an extenderhas heretofore been made.

SUMMARY OF THE INVENTION I It is my discovery that the usefulness of Douglas-fir bark as an extender has been inhibited by reason of the relatively large wax content which is present in natural Douglas-fir bark. I have found that if the bulk of such natural wax is extracted by a solvent the resulting bark provides a very satisfactory extender material that is convenient to use. More particularly, is my discovery that if the wax content of Douglas-fir bark is reduced to below about 3 percent by weight on the basis of the dry bark, the bark makes a very satisfactory extender for thermosetting adhesives in the formation of bonded cellulosic products.

DESCRIPTION OF PREFERRED EMBODIMENT The natural wax content of Douglas-fir bark varies from between about 5 to percent based on the total dry weight of the bark. The exact composition of the wax has not been determined but it is soluble in such usual solvents as hexane or benzene, the chlorinated hydrocarbons, napthalenes, toluene and the like. For the purposes of the invention, the wax content should be reduced below about 3 percent. Suitable extraction techniques will vary, depending upon the nature of the bark being utilized and the solvent selected to extract the wax. However, it has been found that contacting the bark with hexane at its boiling temperature for 3% hours will, for example, reduce the was content of the bark sufficiently to permit use of the bark for an extender.

The wax-extracted bark is primarily useful with phenolic resins such as the phenol-formaldehyde resins but is also adaptable as an extender for other thermosetting resins, such as melamine-formaldehyde and urea-formaldehyde resins.

The amount of extender to be used will vary with the resin, the cellulosic material being bonded, and the desired characteristics of the finished product. In general, however, the extender should comprise between about 5 and 10 percent of the total wet adhesive mix.

Preferably also the bark is rather finely ground, preferably having a fineness so as to pass about a 60-mesh screen. although for certain uses coarser material could be utilized.

With the extender of the invention the conventional pressing and temperatures may be utilized. The assembly time can vary from 3 minutes to 30 minutes but preferably should not exceed about minutes.

EXAMPLE I Douglas-firbark was extracted with hexane at the boiling temperature of the latter for 3 Va hours. The wax content after extraction was less than 3 percent. (This is determined by subjecting a representative bark sample to extraction for another 48 hours and assuming that this results in substantially complete extraction.) The extracted bark was dried and ground so as to pass an -mesh screen. This bark was then mixed to form an adhesive having the following composition:

200 parts Douglas-fir bark 1,340 parts of Hercules p-42 phenolformaldehyde resin 47.0 parts water 60 parts wheat flour 68 parts 50 percent sodium hydroxide 34 parts soda ash Several S-ply Douglas-fir panels were then made up with the above adhesive with wet spreads of 60 pounds adhesive per thousand square feet of double glue line. The panels were pressed at 285 F. and 175 p.s.i. for 4% minutes. Some panels were pressed after 3 minutes and others after 30 minutes of as sembly.

Similar panels were prepared utilizing instead of the Douglas-fir bark, a filler comprising the solid residue remaining after the acid hydrolysis of pentosan-containing materials such as ground-out hulks, the particular material being manufactured by Quaker Oats Company and marketed under the name NORPROFIL,

The panels were then tested for failure of the bond by Commercial Standard Test PS66-l of American NORPROFIL Association with the following results:

In another test three-ply panels with IE Ia-inch face and back and 3/ 16-inch core were prepared from a phenolic resin of a different manufacture using Douglas-fir bark extracted as in example I. The adhesive had the following composition in parts by weight:

200 parts Douglas-fir bark 1,350 parts Chembord Cerac 3l2 phenol-formaldehyde resin 440 parts water 40 parts wheat flour 87 parts 50 percent sodium hydroxide 50 parts soda ash The adhesive was spread at 60 pounds adhesive per thousand square feet of double glue line and pressed at 285 and 175 p.s.i. using different assembly and press times. The results as indicated by Commercial Standard Test ss-ss-l were as follows:

As will be observed, the results are wellabove the requirements of the American Plywood Asociation for exterior plywood which requires an average wood failure of percent with 95 percent showing 80 percent wood failure or higher, 90

percent showing 60 percent wood failure or higher and 97% percent showing 30 percent wood failure or higher.

It is to be understood that other additives such as hardening agents, dyes, and other filler agents can be employed for specific applications. While advantageously employed as plywood adhesives, the adhesives of the invention can be usefully employed with other bonded cellulosic products such as flakeboard, chipboard, hardboard or the like.

Having illustrated and described certain embodiments, it will be apparent that the invention permits of modification in arrangement and detail.

lclaim:

1. An adhesive composition for use in bonding of cellulosic materials comprising a thermosetting resin selected from the class consisting of phenol-formaldehyde, melamine-formaldehyde and urea-fonnaldehyde resins and an extender comprising finely ground Douglas-fir bark having a wax content not in excess of about 3 percent.

2. A composition as set forth in claim 1 wherein said resin is a water-soluble phenol-formaldehyde resin.

3. A composition as set forth in claim 2 wherein said bark comprises between about 5 and 10 percent of the composition.

4. A composition as set forth in claim I wherein said bark has been extracted with boiling hexane for at least 3 5: hours.

5. An extender for use with thermosetting resins comprising finely ground Douglas-fir ,bark having a wax content less than 3 percent.

6. Hot-pressed plywood glued with a bond of a composition as set forth in claim 1.

7. Hot-pressed plywood glued with a bond of a composition as set forth in claim 2.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 616 201 Dated Oct. 26 1971 l fl Frank S. Trocino It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 23, "American NORPROFIL Association" should be -American Plywood \ssociation.

Stiffinwc] 51d 3 1 1 .Lrrd thi :3 1 8th d il of April 1 922 (SI/JAE) Attost:

EDWARD MQI NITCIIQPI, JR. ROBERT GOTTSCHALK Attosti my; Ofii .23: Commissioner of Patents ORM PC3-1 0 (10-69) uscoMM-Dc 60376-P69 a U 5 GOVERNMENT PRINTING OFFICE 7 I959 0-366-334 

2. A composition as set forth in claim 1 wherein said resin is a water-soluble phenol-formaldehyde resin.
 3. A composition as set forth in claim 2 wherein said bark comprises between about 5 and 10 percent of the composition.
 4. A composition as set forth in claim 1 wherein said bark has been extracted with boiling hexane for at least 3 1/2 hours.
 5. An extender for use with thermosetting resins comprising finely ground Douglas-fir bark having a wax content less than 3 percent.
 6. Hot-pressed plywood glued with a bond of a composition as set forth in claim
 1. 7. Hot-pressed plywood glued with a bond of a composition as set forth in claim
 2. 